Original scientific paper
Accuracy of Two Condensation-Type Light Body Silicones after Setting
Marica Šimunović-Šoškić
Zdravko Delić
Abstract
The aim of the study was to determine which dimensional changes occur in two types of low viscosity condensation-type silicone materials (Xantopren - Bayer, Germany and RTV - Bosnalijek, Sarajevo, BiH), when prepared in different conditions (mixed by hand or mechanically, with and without the addition of 3 drops of water) a different time period after setting.
A total of 56 samples were prepared, 7 samples of each silicone (Xsantopren, RTV) in each examined condition (mixed by hand or mechanically, with or without the addition of 3 drops of water). Specimens were poured into a mould until set. The samples were then removed from the mould and stored at room temperature. Using an optical instrument SIP-414 with a digital microscope, dimensional measurements at different time intervals after setting (2, 4, 8 24 and 48 hours) were made. The referent value was the measure of the mould, which was 24.7 mm.
The examined silicone condensation-type impression materials, mixed by hand or mechanically with or without addition of 3 drops of water, showed continuous contraction. The referent value (mould dimension) was greater than all other values measured 2, 4, 8, 24 and 48 hours after setting. The longer the period of sample storage, the greater the silicone contraction. χ2 test revealed that mean values measured in this study are significantly smaller than the referent value, depending on the period of the material storage. Contraction was greater than 0.5% after 2 hours of storage, regardless of mixing condition.
The examined silicone condensation-type impression materials showed significant contraction, which increased during the period of storage, no matter how the material was prepared (mechanically mixed, or by hand; with or without addition of water). The results indicate that silicone condensation-type impressions should be poured into hard stone as soon as possible, to preserve the desired accuracy.
Keywords
condensation-type silicones; low viscosity; dimensional changes after setting
Hrčak ID:
11407
URI
Publication date:
15.9.2001.
Visits: 3.133 *